while (ss.available()) { char c = ss.read(); Serial.print(ss.read()); // Serial.write(c); // uncomment this line if you want to see the GPS data flowing if (gps.encode(c)) // Did a new valid sentence come in? newData = true; }

If the height of geoid is missing then the altitude should be suspect. Some non-standard implementations report altitude with respect to the ellipsoid rather than geoid altitude. Some units do not report negative altitudes at all. This is the only sentence that reports altitude.